Systems and methods for selecting a spectral segment for a transmission

Abstract

The present disclosure generally relates to systems, methods and software for selecting a spectral segment for important downlink and/or uplink transmissions. Particularly, the spectral segment may be a set of contiguous subcarriers within a plurality of subcarriers transmitting over a channel to a population of cable modems. In an embodiment, the systems, methods and software disclosed herein optimize placement of a physical link channel (PLC) within an OFDM channel. In an embodiment, the system, methods and software disclosed herein optimize placement of a ranging region within an OFDMA channel.

What is claimed is: 
     
       1. A method for selecting a frequency window for a transmission over a channel to/from a modem, the method comprising:
 identifying frequency windows sharing a criterion within a profile; and 
 selecting one of the frequency windows for a transmission by:
 (i) choosing the frequency window with a best performance value of the criterion and a broadest frequency range, when the frequency range is equal to or greater than a target frequency range for accommodating the transmission;
 (ii) when no frequency windows have a frequency range equal to or greater than the target frequency range, theoretically combining the frequency window having the best performance value of the criterion with its immediate neighbor frequency window having a second best performance value of the criterion to create a combined frequency window having a combined frequency range at the second best performance value, then choosing the combined frequency window when the combined frequency range is equal to or greater than the target frequency range; or 
 (iii) repeating step (ii) until a combined frequency window with the target frequency range is created. 
 
 
 
     
     
       2. The method of  claim 1 , wherein the frequency range comprises a plurality of contiguous subcarriers. 
     
     
       3. The method of  claim 1 , wherein the criterion is a bit-loading value or a modulation error ratio (MER). 
     
     
       4. The method of  claim 1 , wherein the profile is a least-common-denominator profile. 
     
     
       5. The method of  claim 4  further comprising generating the least-common-denominator profile for a population of modems. 
     
     
       6. The method of  claim 5 , wherein the step of generating the least-common-denominator profile comprises:
 receiving channel measurement data from each modem of the population for each of a plurality of subcarriers within the frequency range; 
 calculating, from the received channel measurement data, a performance value for each modem per subcarrier; and 
 converting the performance value for each modem per subcarrier into a performance value for the population of modems per subcarrier to obtain the least-common-denominator profile. 
 
     
     
       7. The method of  claim 6 , wherein the received channel measurement data is downlink or uplink modulation error ratio (RxMER) data, noise data, carrier suppression data, or distortion data. 
     
     
       8. The method of  claim 6 , wherein the performance value is a bit-loading value or a modulation error ratio (MER). 
     
     
       9. The method of  claim 1  further comprising optimizing placement of the transmission within the frequency window. 
     
     
       10. The method of  claim 9 , wherein the transmission is placed at a midpoint of the selected frequency window or shifted away from interference occurring near an edge of the selected frequency window. 
     
     
       11. The method of  claim 10 , wherein the placement of the transmission is calculated by weighting interference at both edges of the selected frequency window. 
     
     
       12. The method of  claim 1 , wherein the transmission is a downlink transmission or an uplink transmission. 
     
     
       13. The method of  claim 12 , wherein the downlink transmission is selected from the group consisting of a physical link channel (PLC) or a logical control channel. 
     
     
       14. The method of  claim 12 , wherein the uplink transmission is selected from the group consisting of a ranging region or a logical control channel. 
     
     
       15. The method of  claim 1 , wherein the modem is a cable modem. 
     
     
       16. A method for selecting a segment within a plurality of subcarriers for a transmission over a channel to/from a modem, the method comprising:
 identifying segments of contiguous subcarriers within a profile having the same bit-loading value; and 
 selecting one of the segments for a transmission by:
 (i) choosing the segment with the highest bit-loading value and the widest range, when the width of the segment is equal to or greater than a target width; 
 (ii) when no segments have a width equal to or greater than a target width, theoretically combining the segment having the highest bit-loading value with its immediate neighbor segment having a next highest bit-loading value to create a combined segment having a combined width at the next highest bit-loading value, then choosing the combined segment when the combined width is equal to or greater than the target width; or 
 (iii) repeating step (ii) until a combined segment with the target width is created. 
 
 
     
     
       17. The method of  claim 16 , wherein the profile is a least-common-denominator profile generated by:
 receiving channel measurement data from each modem of the population for each of the plurality of subcarriers; 
 calculating, from the received channel measurement data, a maximum bit-loading value for each modem per subcarrier; and 
 converting the maximum bit-loading value for each modem per subcarrier into a maximum bit-loading value for the population of modems per subcarrier to obtain the least-common-denominator profile. 
 
     
     
       18. The method of  claim 16 , further comprising optimizing placement of the transmission within the segment. 
     
     
       19. The method of  claim 18 , wherein the transmission is placed at a midpoint of the selected segment or shifted away from interference occurring near an edge of the selected segment. 
     
     
       20. The method of  claim 19 , wherein the placement of the transmission is calculated by weighting interference at both edges of the selected segment.